Boil the ramen noodles according to the package instructions. Drain and rinse with cold water to prevent sticking.
Heat a skillet or wok over medium-high heat. Add olive oil, chicken (if using), onion, salt, and pepper. Cook for 3-4 minutes until the chicken is cooked through.
Stir in the minced garlic and cook for 1 minute until fragrant.
Add the cooked noodles to the skillet, followed by the Japanese BBQ sauce, soy sauce, sriracha, and butter. Stir to coat the noodles evenly.
Press the noodles into the skillet and cook for 5-7 minutes, stirring occasionally, until slightly crisped.
Add the sliced green onions and cook for an additional 1-2 minutes.
Serve hot, garnished with sesame seeds, extra BBQ sauce, or yum yum sauce if desired.